気中放電加工における工具電極微消耗のメカニズム

抄録

This paper clarifies the reasons for the minute tool electrode wear in the dry EDM. In the dry EDM, which has been newly developed, a high velocity gas flow supplied through a thin-walled pipe electrode removes and flushes the molten workpiece material out of the working gap without allowing it to reattach to the electrode surfaces. The greatest advantage of this technique is that the tool electrode wear is almost negligible for any pulse duration. It is thought that the attached molten workpiece material protects the tool electrode surface against wear. That is, the molten workpiece that has a higher melting point than that of the tool electrode adheres to the surface of the tool electrode that has a higher thermal conductivity than the workpiece. To verify this idea, the influence of the layer thickness of the workpiece material precipitated on the tool electrode surface on the temperature distribution in the tool electrode was numerically analyzed Then the tool electrode wear was simulated based on the result of the above heat conduction analysis. From observation of the cross section of the tool electrode surface, it was found that the tool electrode wore by the depth of only 2 μm during the early stage of successive pulse discharges since the initial surface of the tool electrode was not covered with the steel layer. As the thickness of the steel layer increases, however, the wear of the base metal of the tool electrode ceases in one minute and thereafter the layer thickness is kept constant at 8.5 μm. These experimental results coincide well with the simulation results.